Method of preparing soybean products free of antitrypsin

ABSTRACT

1. A METHOD FOR PREPARING SOYBEAN PRODUCTS FREE OF ANTITRYPSIN, COMPRISING CRUSHING UNEXTRACTED SOYBEANS CONTAINING UREASE, THE HYMIDITY OF THE CRUSHED GRAINS BEING AT MOST 12%, SPRAYING THE CRUSHED SOYBEANS WITH AN AQUEOUS SOLUTION OF UREA, THE AMOUNT OF UREA BEING BETWEEN 0.1 AND 0.4 PART PER 100 OF THE SOYBEANS BY WEIGHT, ROLLING THE SPRAYED SOYBEANS TO OBTAIN FLAKES THEREBY IMPROVING THE DISTRIBUTION OF UREA, THE TEMPERATURE OF THE SOYBEANS PRIOR OF ROLLING BEING NO HIGHER THAN 70* C., AND THEN COOKING SAID FLAKES IN STEAM WITH THE HUMIDITY OF THE FLAKES BEING 18-20% AT 100-110*C. UNTIL DESTRUCTION OF ANTITRYPSIN IS OBTAINED.

United States Patent 3,845,229 METHOD OF PREPARING SOYBEAN PRODUCTS FREEOF ANTITRYPSIN Michel Rambaud, Paris, France, assignor to SocieteIndustrielle des Oleagineux, Paris, France No Drawing. Continuation ofabandoned application Ser. No. 841,563, July 14, 1969. This applicationMar. 27, 1972, Ser. No. 238,712

Int. Cl. A23] 1/20 US. Cl. 426-375 6 Claims ABSTRACT OF THE DISCLOSURESoybean cooking process by carrying out the cooking at a pH below 9preferably 8.0-8.5 at a temperature of 100- 110 C., for extracted orunextracted soybeans.

This application is a continuation of copending application Ser. No.841,563, filed July 14, 1969 and now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to the treatment of soybean by cooking, both are extracted andoil unextracted soybeans.

2. Description of the Prior Art It is known in fact that the reason forthe poor alimentary value of soybeans is the presence therein ofundesirable compounds, the most important of which is antitrypsin.Considerable research has been done with a view to achieving thedestruction of anti-trypsin, which inhibits tryptic proteolysis and,even in small doses, produces harmful secondary reactions.

It has now been found that antitrypsin disappears from oil extracted andunextracted soybeans when they are subjected to high temperaturecooking, particularly steam cooking. This treatment however is not freefrom disadvantages.

If the cooking is effected at too high a temperature or if it isprolonged with a view to destroying antitrypsin, this treatment givesrise to excessive denaturation of the proteins, a reduction of thesolubility of the latter in water, and an increase of soda insolublematter.

It is for this reason that it has been found necessary to establishcooking standards which preserve the proteins.

The studies carried out by the applicant have however revealed that withthese standards the complete destruction of antitrypsin is not achieved.The cooked products still contain antitrypsin, and this comprises notonly the quantity which can be determined by usual methods but inaddition a considerable amount which can be detected after carefulhydrochloric treatment.

Determinations made have shown that this amount of antitrypsin which canbe detected after hydrochloric treatment was of the order of 2% of theoriginal antitrypsin in the product. It is clear that, in vivo, duringstomachal digestion of the soybeans this antitrypsin will be liberatedby rennet or pepsin, so that the alimentary value of the product isreduced.

In order to overcome these difiiculties the applicant proposed in US.Pat. No. 3,220,851 a method of treatment, particularly for soybeans,which consists in effecting careful cooking under defined conditions ofconcentration, while maintaining the pH at a value close to 9 in aliquid medium. This method gives excellent results and leads to thecomplete destruction of the antitrypsin but it is relatively complex tocarry out.

The main object of the present invention is to provide a method oftreating soybeans by cooking which overcomes these disadvantages andleads to a product of high alimentary value which is substantially freefrom anti- 3,845,229 Patented Oct. 29, 1974 ice trypsin, even asrevealed after hydrochloric treatment, by simple means which werecapable of use in traditional soya oil works without modifying equipmentor substantially increasing cost of manufacture.

SUMMARY A method of processing unextracted soybeans for elim inating theantitrypsic factor, comprising adjusting the pH value of the soybeans to8-9 by means of an alkalizing reagent, the amount of alkalizing reagentbeing for parts of soybeans by weight, treating the soybeans with steamto raise the temperature of the soybeans to 100- C. and cooking thesoybeans at this temperature.

The humidity necessary for the reaction of destroying the antitrypsin isprimarily supplied by the condensation of the steam and the duration ofthe cooking treatment will depend on this humidity, which in turn isdependent on whether or not oil has been extracted, because it isnecessary to supply the heat of evaporation of the solvent.

Adjustment of the pH value entails the addition of an alkalizing reagentby spraying of a concentrated suspension or solution over the crushedgrains, the humidity of which is at most 12%, thus enabling the reagentto be distributed uniformly during the rolling, an operation whichnormally follows the crushing and in the course of which flakes of athickness of 20 to 40 hundredths of a millimetre are obtained.

The reagent used may for example be a caustic soda or ammonia solutionor milk of lime. The amounts used per 100 parts of beans are:

NaOH-O.1 to 0.6, preferably 0.3 CaO0.l to 0.5, preferably 0.2 NH -0.05to 0.4, preferably 0.15.

The amount of water, the reagent vehicle, represents less than 2% of theweight of the soybeans, generally 1% or less.

Another method which has been found advantageous comprises spraying asolution of urea over the starting material. If, in particular, crushedsoybeans are used for this operation, the sprayed urea is distributed inthe soybean during the rolling which normally follows the grinding. Thenatural urease of the beans converts the urea into ammonia by enzymaticaction in actual contact with the proteins, and thus with theantitrypsin to be inactivated, thus raising the pH of the material byammoniacal alkalisation within the material itself. The urease is notinactivated unless the soybean is heated to a temperature higher than 70C. before rolling.

The use of urea prevents any accidental local overalkalisation whichmight degrade the sulphur amino acids, because the enzymatic reactionslows down itself when the pH is too high. The amount of urea is from0.1 to 0.4% by weight referred to the amount of soybean, preferably 0.2.to 0.3%. The urea solution is preferably in a concentration of from 30to 50% by weight.

The conditions of the thermal treatment the essential aim of which isthe destruction of the antitrypsin vary depending on whether it isdesired to produce extracted or unextracted soybean meal.

In the case of oil extracted soybean the flakes impregnated with essencewhich leave the extractor are at a temperature of 50 C., and the steamtreatment rapidly brings them up to the temperature of 65 C., theboiling point of hexane, and then after the disappearance of the solventthe temperature rises to 100-110 C., humidity then attaining 22-25%.Starting from this moment, cooking for less than 1-0 minutes issufficient to bring about the destruction of the antitrypsin. The cookedde-oil extracted is then dried.

In the case of unextracted soybean, the flakes leaving the rolling millat a temperature of about 40 C. are

3 subjected to the action of steam. Their temperature is raised to ll10C., their humidity then being 18-20%, and the duration of the thermaltreatment starting from this point will be less than 20 minutes. Thecooked unextracted soybeans are then dried.

It should be noted that when urea is used, the urease in the soya whichwill alkalize the product by decomposition of urea is not destroyed whenoil is extracted, nor is it destroyed by heat as long as the temperaturedoes not reach 70 C., and when the destruction of the urease has beenelfected the urea has already been completely converted. The residualdoses of urea and ammonia in the final product are very slight and of noimportance for feeding purposes.

Another method of alkalizing soybean consists in mixing gaseous ammoniawith the cooking steam, this ammonia being eliminated during the drying.It is also possible for a plurality of these methods of alkalization tobe used simultaneously.

The product obtained will no doubt not have all the properties of thatresulting from the process of U.S. Pat. No. 3,220,851, and in particularit will have lower solubility. Nevertheless, the product of thisinvention has digestibility equivalent to that obtained in accordancewith US. Pat. No. 3,220,851.

Unlike the previous process of the applicant, in which a pap of soybeanis treated, the process of the invention destroys antitrypsin inslightly moist products, using water contents close to those used intraditional oil works, without using special installations and thereforewithout giving rise to special expense for drying, as is the case invarious other known processes, which do not however bring about thecomplete destruction of antitrypsin.

EXAMPLES OF THE PREFERRED EMBODIMENTS The invention will now be furtherdescribed with reference to the following Examples.

EXAMPLE 1 Soybean cooked with lime in a non-continuous oil extractioninstallation.

This conventional method of non-continuous soybean extraction (batchprocess) comprised the following operations:

(l) Crushing the soybeans in a fluted cylinder grinder.

(2) Passing the crushed soybeans through a plate type heater or heatingworm enabling the crushed grain to be heated and, if required, slightlyhumidified by steam or by spraying of water so as to increase itsplasticity.

(3) Rolling the soybean between cylinders so as to burst the vegetablecells and obtain the bean in the form of flakes, while avoiding theproduction of flour.

(4) Methodical extraction in a battery of extractors working by thebatch process with the aid of a solvent, which is generally hexane.

(5) After the oil had been extracted by the solvent, the

extractor at the top of the battery was drained of sol- 'vent and steamwas injected beneath the false bottom of the extractor to effect theevaporation of the solvent with which the cakes were impregnated. Theinjection of water vapour was continued for about minutes after nofurther solvent vapour was entrained by the steam. In this manner, thetop layers in the extractor were cooked with steam at 100105 C. for 10minutes with a humidity of 22-25%, while the bottom layers had beencooked for a longer time, which could be as much as 40-50 minutesbecause of the time necessary for the evaporation of the solvent step bystep from bottom to top.

In the method of the invention lime was introduced as a spray of milk oflime into the heating worm between the crushing and the rolling of thesoybeans. The lime was introduced with a dosage of 0.2% of the weight ofthe soybeans, in the form of milk of lime containing 1 kg. oi" lime per9 kg. of milk of lime.

When extracted in the cold state in the laboratory, the soybeans usedyielded a meal containing 4% of antitrypsin.

An average sample of soybean meal obtained without addition of limestill revealed 0.1% of antitrypsin after hydrochloric treatment, that isto say 2.5% of the original antitrypsin in the soybeans, so that therate of destruction of antitrypsin amounts to 97.5%.

Longer cooking did not improve this rate.

Because of the incorporation of lime, antitrypsin was no longer detectedin the cake and the rate of destruction of antitrypsin consequentlyattained EXAMPLE 2 The operation was carried out in the same manner asin Example 1, but instead of milk of lime a solution of urea was sprayedon over the crushed beans, heated, to 40 C. The urea was used with adosage of 0.3% referred to the weight of the soybeans and was used inthe form of an aqueous solution with a concentration of 30%.

100% destruction of antitrypsin was'likewise achieved and the soybeanmeal obtained contained practically no urea and an amount of ammoniaonly slightly larger than the amount naturally present in soybean meal.

EXAMPLE 3 With the object of obtaining cooked unextracted soybean thesame equipment as that usedin Examples land 2 was employed for theoperations of crushing and rolling. The rolled soybeans contained in theextractor were treated directly with water vapour, without solventtreatment, and cooking was continued for 15 minutes after the watervapour has heated the mass of beans and humidified it and escaped freelyinto the top part of the extractor. Under these conditions, thetemperature of the beans rose to 100-105 C. and the humidity of thebeans was brought to 1820%.

If an alkalizing product was not incorporated, the cooked soybeanscontained about 0.1% of antitrypsin, determined as in Example 1. v 1

By the invention, urea was incorporated under the same conditions as inExample 2. 100% destruction of antitrypsin was then achieved.

EXAMPLE 4 I The soybeans were prepared by crushing and rolling in thesame manner as in the previous Examples. They were treated in acontinuous extraction installation and the soybean meal was cooked atthe same time as the solvent was eliminated in an apparatus of the typeconventional in oil works and which is known as a desolventiser-toaster.

If no alkalizing agent was incorporated, the heating and injection steamwas adjusted in. the desolventisertoaster in such a manner that. thesoybean meal leaves with a humidity of 13% and a temperature of C., withan antitrypsin content of 0.1% determined as in Example 1.

Incorporation of urea in accordancewith theinvention with a dosage of0.25% by spraying in thezform of.a 40% aqueous solution during theheating to 40 C. of the soybeans in the heating worm between thecrushing and grinding operations brought the residual content ofantitrypsin to zero.

EXAMPLE 5 unextracted, dehulled soybeans were used, which were crushedand rolled as in the previous Examples, while before the grinding of 40%solution of urea was sprayed on the crushed soybeans at a temperature of35 C. in a proportion such that the rate of incorporation of urea in thebeans was 0.2%.

The same continuous extraction equipment was used as in Example 4, butwithout using a solvent, so that the continuous extractor served only totransport the rolled soybeans to the desolventiser-toaster.

The heating and injection steam were adjusted in thisdesolventiser-toaster in such a manner that the soybeans impregnatedwith urea were brought on the top trays to a humidity of 18-20% and to atemperature of 100- 105 C. and dried at 105-110 C. on the bottom trays,the passage time in the apparatus being about 30 minutes.

The use of urea made it possible to achieve 100% destruction ofantitrypsin, whereas if urea were not used only about 97% of theantitrypsin would be destroyed.

EXAMPLE 7 The operation was carried out under the same conditions as inExample 6, by-passing the continuous extractor by using a conveyor worm.

I claim:

1. A method for preparing soybean products free of antitrypsin,comprising crushing unextracted soybeans containing urease, the humidityof the crushed grains being at most 12%, spraying the crushed soybeanswith an aqueous solution of urea, the amount of urea being between 0.1and 0.4 part per 100 of the soybeans by weight, rolling the sprayedsoybeans to obtain flakes thereby improving the distribution of urea,the temperature of the soybeans prior to rolling being no higher than 70C., and then cooking said flakes in steam with the humidity 6 of theflakes being 18-20% at 100-110 C. until destruction of antitrypsin isobtained.

2. A method as claimed in claim 1, wherein said amount of urea isbetween 0.2 and 0.3 part per 100.

3. A method as claimed in claim 1, wherein said flakes are cooked for nomore than 20 minutes.

4. A method for preparing soybean products free of antitrypsin,comprising crushing unextracted soybeans containing urease, the humidityof the crushed grains being at most 12%, spraying the crushed soybeanswith an aqueous solution of urea, the amount of urea being between 0.1and 0.4 part per 100 of the soybeans by weight, rolling the sprayedsoybeans to obtain flakes thereby improving the distribution of urea,the temperature of the soybeans prior to rolling being no higher thanC., extracting oil from said flakes, and then cooking said flakes insteam with the humidity of the flakes being 22-25% at C. untildestruction of antitrypsin is obtained.

5. A method as claimed in claim 4, wherein said amount of urea isbetween 0.2 and 0.3 part per 100.

6. A method as claimed in claim 4, wherein said flakes are cooked for nomore than 10 minutes.

References Cited UNITED STATES PATENTS 3,155,524 11/1964 Norris et a1.99.38 3,220,851 11/1965 Rambaud 99-98 2,848,342 9/ 1958 Atkinson 106-l54RAYMOND N. JONES, Primary Examiner US. Cl. X.R. 426-377, 364

1. A METHOD FOR PREPARING SOYBEAN PRODUCTS FREE OF ANTITRYPSIN,COMPRISING CRUSHING UNEXTRACTED SOYBEANS CONTAINING UREASE, THE HYMIDITYOF THE CRUSHED GRAINS BEING AT MOST 12%, SPRAYING THE CRUSHED SOYBEANSWITH AN AQUEOUS SOLUTION OF UREA, THE AMOUNT OF UREA BEING BETWEEN 0.1AND 0.4 PART PER 100 OF THE SOYBEANS BY WEIGHT, ROLLING THE SPRAYEDSOYBEANS TO OBTAIN FLAKES THEREBY IMPROVING THE DISTRIBUTION OF UREA,THE TEMPERATURE OF THE SOYBEANS PRIOR OF ROLLING BEING NO HIGHER THAN70* C., AND THEN COOKING SAID FLAKES IN STEAM WITH THE HUMIDITY OF THEFLAKES BEING 18-20% AT 100-110*C. UNTIL DESTRUCTION OF ANTITRYPSIN ISOBTAINED.